In recent year, the Internet has been intergraded into many aspects of our lives, and faces following problems. Even if we can use the Internet at home, in the office, and in public spaces, it is difficult to newly install a wired local area network (hereinafter simply referred to as “wired LAN”) in an ordinary and old house. Further, the wired LAN is unfit for a mobile computer to be carried if necessary. On the other hand, a wireless local area network (hereinafter simply referred to as “wireless LAN”) using relatively expensive network equipments such as network interface card, router and the like is fit for the mobile computer. We think that the wireless LAN, which meets consumer demand for convenient items and the like, will be widely used in the future in comparison with the wired LAN.
No one knows for sure that the wireless LAN exceeds the wired LAN. The wireless LAN is relatively expensive, and faces following problems. The conventional wireless LAN has a weak side regarding network security. In the wired LAN, the network manager can checks visible lines between network equipments. On the other hand, the network manager cannot check an invisible connection between a network point and a wireless terminal device in the wireless LAN, and cannot detect a wireless terminal device for surreptitious interception at a glance. Therefore, the wireless LAN is required to have a high protection function for preventing information transferred between clients and servers from being intercepted. It is preferred that the network manager skilled in the art register wireless LAN terminal devices to be connected to the access point by wireless, and set the name of the access point and a cryptography key, and routinely checks access log recorded in the access point to detect improper use of the network.
Therefore, it is not a good idea to expect a user to manage a local area network installed in his/her home. In order to put a wireless LAN into every home, the wireless LAN system is required to simply set information needed for encryption and authentication.
The above-mentioned conventional wireless LAN system has a wireless LAN terminal device and an access point. When the access point is ON, the access point can receive only an initial setting packet transmitted from the wireless terminal device, the access point produces and registers a wired equivalent privacy key (hereinafter simply referred to as “WEP key”) the same as that of the wireless terminal device (see, for example, patent document 1).
Patent document 1: Japanese Patent Laid-Open Publication 2005-142907